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Page 18 of 24 Yu et al. Soft Sci. 2026, 6, 19

The grasping protocol is shown in Figure 5B, with test objects including a turtle (28.3 g), jellyfish model
(18.5 g), sea cucumber model (33.9 g), mineral model (54.1 g), and algal sphere (8.6 g). Although the turtle
used in this study are shallow water species, the sea cucumber and jellyfish models employed in the grasping
tests have smooth surfaces and soft textures, and therefore can serve as reasonable proxies for deep-sea
organisms. The mineral model used in the experiments was collected from seawater at a depth of 5,566.7 m
and thus can be used as a representative deep-sea mineral target for grasping trials.

The procedure was as follows: Step 1, the robotic arm was positioned 30 mm above the target with the coil
de-energized, leaving the gripper relaxed; Step 2, upon reaching the designated position, a reverse current
was applied, generating an upward magnetic field that induced outward expansion of the gripper to increase
the capture probability; Step 3, the arm descended until the gripper enclosed the target, after which a forward
current was applied, producing inward contraction for grasping; Step 4, the current was maintained to
ensure a stable magnetic field during secure grasping, while the arm transported the object to the designated
location; Step 5, finally, the current was switched off to release the target, completing one grasping cycle
[Supplementary Movies 8-12]. Each object was tested in ten repeated trials to ensure statistical reliability. As
shown in Figure 5B, the gripper’s magnetic response speed during grasping was consistent with earlier
dynamic tests, confirming rapid actuation during underwater manipulation. Post-experiment inspection
revealed no structural damage to any object: the turtle continued normal swimming after release, and the
algal sphere remained intact, verifying that the MSG achieved non-destructive grasping.

Experimental results and discussion: The above results demonstrate that the MSG exhibits high reliability,
versatility, and safety in complex underwater environments, characterized by rapid response, damage-free
manipulation, and strong disturbance resistance. Compared with conventional actuated grippers, the
magnetic actuation strategy significantly shortened the expansion-contraction response time, thereby
improving overall grasping efficiency. Moreover, the gripper reliably handled spherical, elongated, and
irregularly shaped targets, while ensuring non-destructive manipulation of delicate biological samples (e.g.,
live turtles). With its combination of fast response and soft, safe contact mechanics, the MSG shows strong
potential for efficient and non-destructive grasping of dynamic biological targets in marine applications.

Exploration of deep-sea grasping performance
To assess the applicability of the proposed MSG in deep-sea conditions, this study following baseline
experiments at ambient pressure and temperature further conducted two sets of experiments (high pressure
and low temperature) to simulate extreme operational conditions and to verify the reliability and
functionality of the MSG. The experimental procedures and results are summarized below.

High pressure experiments: To mimic the extreme hydrostatic pressure of the deep sea, a sealed
high-pressure chamber was pressurized by water injection to a constant pressure of 60 MPa, corresponding
to conditions at approximately 6,000 m water depth. The experimental setup is shown in Figure 6A. The
procedure was as follows: the chamber was filled with water; a preprepared set of MSGs was placed inside
and the chamber was sealed; water was subsequently added until the internal pressure reached 60 MPa,
which was maintained for 2 h. After depressurization and retrieval, each MSG underwent an external
structural inspection and a residual magnetic induction measurement using a magnetometer, as shown in
Figure 6B. Across repeated trials, no structural failure was observed. The mechanical and magnetic properties
of the MSGs after high pressure exposure differed from their pretest values within the range of experimental
measurement uncertainty and acceptable limits, indicating that short term exposure to high static pressure
does not cause significant adverse effects on the MSG developed in this study.